Cleaning and preserving of metallic surfaces



Patented June 2, 1931 UNITED STATES PATENT OFFICE DEAL H. TOMPKINS, OFNITRO, WEST VIRGINIA, ASSIGNOR TO THE RUBBER SERVICE LABORATORIESCOMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO CLEANING AND PRESERVINGOF METALLIC SURFACES No Drawing.

invention relates to the prevention of excessive pitting andembrittlement of a metal when subjected to a pickling process.

Certain objects of the invention are to pre- Vent the acid pickle liquorfrom attacking clean portions of the surface of a metal; to

obviate over-pickling, embrittlement and pitting of the articlestreated; to minimize the amount of metal lost in pickling; to increasethe efficiency of the pickling operation and to prolong the effectivelife of the pickling bath and particularly to speed the picklingoperation. Other and further objects of the invention will be apparentfrom the following description and accompanying examples.

In the art of pickling, the metal is treated with a dilute acid toremove oxides such as rust, scale, and other deposits, after which themetal is preferably washed with water and dipped into analkaline bath toremove the last traces of free acid. The acid removes the rust andscale, but unfortunately, from the pickling standpoint, it attacks thecleaned metal itself thereby causing loss of metal and producing anevolution of hydrogen gas, which escapes into the air, carrying with ita line spray of the pickling bath and producing an atmosphere possessingcorrosive properties and one which is highly injurious to health.

By the present invention, these objectionable features of the picklingprocess are substantially overcome or reduced to a minimum. Toaccomplish the objects set forth in accordance with the presentinvention, there is added to the pickling bath a regulating agent oringredient which acts to restrain the action of the acid from attackingclean metal but assists in removing the rust, scale and other deposits,or in other words'it selectively removes such materials withoutappreciably attacking the clean portions of the metal.

The pickle regulator or inhibitor, as disclosed in the presentapplication, comprises a sulfuric agidderilative of a reaction productoisuldioxide and an aldehyde-amine re- Application filed June 30,

1930. Serial No. 465,070.

action product and preferably a sulfuric, acid derivative of a reactionproduct of sulfur dioxideland an aldehyde derivative of' a Schifis base;that is, a product formed by reacting an aldehyde with a Schifi"s base,adding sulfur dioxide thereto and treating the-product so formed withsulfuric acid of any concentration necessary to produce sulfonation atthe reaction temperature employed.

In the examples hereinafter set forth for carrying out the metalpickling process, con-' ditions were imposed which duplicated, so far aspossible, those commonly followed in commercial practice, so far asconcerned acid concentrations and temperatures employed;

Test pieces of steel approximately 4 x 3", gauge hot rolled tin platestock were then immersed in approximately 500 c. c. ofa water solutionof sulfuric acid containing approximately 8% by weight of 66 B. acid towhich had been added a small quantity of one of the preferred type ofinhibitors. The loss in weight of the steel test pieces resulting frommaintaining the strips in the pickle bath in the manner described for adefinite period of time was then determined. The temperature of thepickling bath was maintained at from 176 to 185 F. (80 to 85 C.). Forthe acid concentration set forth, commercial practice is to pickle atapproximately 150 to 190 F. (66 to 88 (3.). The results so obtained werecompared with similar tests wherein the steel pieces were subjected,under the conditions set forth, to the action of an acid solution of thestrength and for the time specified above, but containing no inhibitor.

One method whereby one of the preferred class of compounds, for examplea sulfuric acid derivative of the reaction product of sulfur dioxide andan aldehyde derivative of a Schiifs base, was prepared as follows:

Substantially one molecular proportion of the product formed from thereaction of substantially three molecular proportions of acetaldehydeand substantially two molecular proportions of aniline, according to themethod set forth in U. S. Patent No. 1,659,152 granted to Clayton OlinNorth, was dissolved in an organic solvent, for example, a quantity ofacetone equal to one-third of the weight of the aldehyde-amine product.Substantially one-half a molecular proportion of sulfur dioxide waspassed thereinto at a rate slow enough for complete absorption andcombination to take place while agitating and maintaining a temperatureof approximately 30 to C. To the product thus formed, substantially onemolecular proportion of sulfuric acid, preferably having an acidstrength of 75% was added at a temperature of substantially 50 to C.After the addition of the sulfuric acid was completed, the water presentand the solvent employed, for example acetone, were removed preferablyby evaporation. The product prepared in the manner described, aftercooling'was a brittle resin, which formed a fine powder when ground thatwas readily soluble in a pickle liquor as for example dilute sulfuricacid. A sample of the material prepared as described above wasincorporated in a pickling bath in the manner hereinbefore described.Thus a steel test piece 3 x 4", 30 gauge hot rolled tin plate stock,exposing 24 square inches of surface and weighing 17.5228 grams, wasfound to lose but 0.017 3 grams after 20 minutes pickling in an 8%sulfuric acid solution containing 0.12 grams of the inhibiting productjust described. A similar test piece weighing 17.0100 grams and treatedin the same manner, but without the use of any inhibitor lost 0.2997grams.

Thus, when the sulfuric acid derivative of the reaction product ofsulfur dioxide and the product formed by reacting substantially threemolecular proportions of acetaldehyde and substantially two molecularproportions of aniline is employed as an inhibitor, the loss in weightper square inch of surface exposed corresponds to 0.00072 grams whereaswhen no inhibitor is used the loss per square inch of surface exposedcorresponds to 0.0125 grams. A greater saving in metal losses resultsfrom the use of a larger amount of the inhibitor. Moreover, the steelplates pickled in the presence of the inhibitor set forth are clean andnot stained upon removal from 60 to 70 C. To the product so formedapproximately one molecular proportion of sulfuric acid having anacidity of approximately was added with agitation at a temperature ofapproximately 90 to 100 C. A sample of the above identified material wasincorporated in a sulfuric acid pickling bath in the manner previouslydescribed. The following table shows a comparison between the loss inweight of the test strips, after immersion in the pickling bath fortwenty minutes, when the inhibitor just described was employed and whenno inhibitor was employed.

Table I 3" x 4", 30 gauge hot rolled tin plate stock pickled twentyminutes in 8% sulfuric acid at C.

Average loss with inhibitor 0.000391 grams per sq. in.

Average loss without inhibitor 0.012491 grams per sq. in.

From the results set forth in Table I it is apparent that the averageloss in weight when no inhibitor is employed is approximatelythirty-four times greater than the average loss resulting when theinhibitor set forth is employed in the pickle bath described.

Other sulfuric acid derivatives of the reaction products of sulfurdioxide and aldehyde-amine products, and preferably sulfuric acidderivatives of the reaction products of sulfur dioxide and aldehyde.derivatives of Schifi"s bases have been prepared in a manner analogousto that hereinbefore set forth and tested as inhibitors in a picklingbath in the manner described.

Thus, the sulfuric acid derivatives of the sulfur dioxide reactionproducts of a Schiifs base and of aldehyde derivatives thereof as setforth hereinafter were prepared and the final product so obtainedempolyed in a pickling bath and tested in the manner described. Theproducts referred to in the results set forth in Table II, as inhibitorsA to G inclusive, represent the sulfuric acid derivatives of the sulfurdioxide reaction product of the following bases:

Oompownd A.Substantially three molecular proportions oftacetaldehydeaiidtwo molecular proportions of orthgtoluidine.

252. COMPOSITIONS,

ular proportions of butylalglebyde and one molecular proportion ofortho-toluidine.

Table II 3 x 4", 30 gauge hot rolled tin plate stock pickled twentyminutes in 8% sulfuric acid at 80 C.

' i w h r w in f 'eig to eig of oss in gh gai -Ea steel strip steelstrip grams per poun mp 0y em 10 ed before after sq. inch of p ypickling pickling surface exposed I Grams Grams Grams Grams Compound A.O. 12 16. 672 16:655 0. 00071 Compound B- 0. 12 16. 810 16. 798 0.(-0050 Compound C- 0. 12 17. 342 17. 336 0. 00025 Compound D. 0. 12 17.122 17. 101 0. 00087 Compound E... .12 16. 655 16. 649 0. COCZS CompoundF. 0. 12 17. 503 17. 496 0. 00029 Compound (3.. 0. 12 16. 620 16. 604 0.00058 None l None. 17.0100 16. 7103 0. 01242 It is thus apparent fromthe data set forth that the preferred class of materials constitute animportant group of inhibitors, as in all cases where one of thepreferred inhibiting compounds was incorporated in the pickle liquor,there resulted a metal saving of from 96 to over 98% of the loss inweight of the steel test strips that resulted when no inhibitor wasemployed.

The preferred class of inhibiting compounds has also been employed inother pickling baths than sulfuric acid wherein materials 0' her thaniron and steel were pickled. The following example illustrates onemethod of pickling a nickel chromium alloy, wherein one of the preferredinhibitors, for example, the product formed by treating the reactionproduct of sulfur dioxide and the aldehyde-amine product prepared fromsubstantially three molecular proportions of acetaldehyde andsubstantially two molecular proportions of aniline with sulfuric acid inthe manner previously described, was employed as an inhibitor in ahydrochloric acid pickling bath.

A piece of nickel chromium alloy wire having a composition of 80% nickeland 20% chromium, 36 inches in length, 0.036 inches in diameter, havinga total surface of 4.07

Hammer square inches and weighing 5.2640 grams, was coiled in the formof a spiral and immersed in approximately 500 grams of 17% hydrochloricacid containing 0.24 grams of the product formed by treating thereaction product of substantially three molecular proportions ofacetaldehyde and substantially two molecular proportions of aniline withsulfur dioxide and further reacting said prouct with sulfuric acid inthe manner hereinbefore described. After allowing the wire to, remain inthe pickle liquor for 20 minutes at 176 F., the loss in weight was foundto be only 0.0405 grams. A test identical with that described above withthe exception that the nickel-chromium wire weighed 5.3225 grams and noinhibitor was employed, showed a loss of 0.2060 grams. words the weightloss due to solvent action of the hydrochloric acid on the metal wasonly one-fifth as great when the preferred inhibitor was employed as wasthe loss with no inhibitor present. A greater saving in metal would berealized by employing a greater proportion of the inhibitor.

It has further been found that other ratios In other of sulfuric acid,sulfur dioxide and aldehydeamine than those hereinbefore set forth maybe reacted and employed as inhibitors. Thus substantially one molecularproportion of the aldehyde derivative of a Schiifs base formed byreacting substantially three moleoular proportions of acetaldehyde withsubstantially two molecular proportions of aniline has been reacted withvarying amounts of sulfur dioxide preferably in the ratios betweensubstantially one-fifth to one molecular proportion and the material soprepared further reacted with varying concentrations of sulfuric acidpreferably in ratios varying between three-fourths to one and one-halfmolecular proportions. In all cases the materials so obtained, onincorporating in a pickle bath and testing in the manner hereinbeforeset forth, were found to be very prepared in a benzene medium and theresulting material on testing found to be a very desirable inhibitor.

Other modes of employing inhibitors of the type set forth herein in theacid pickling of metals are apparent to those skilled in the 3;:

art to which this invention pertains. The products describedadditionally may be employed in the pickling process in the presence offoaming agents, ionizable substances or other materials ordinarily used.

\Vhat is claimed is: 1. A process of pickling iron and steel productswhich comprises subjecting the metal to be pickled to the action of asulfuric acid solution containing a small proportion of a sulfuric acidderivative of a reaction product of sulfur dioxide and an aldehydeamineproduct.

2. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a sulfuric acid derivative ofa. reaction product of sulfur dioxide and an aliphaticaldehyde-aromatic-amine reaction product.

3. A process of pickling iron and steel prodacts which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a sulfuric acid derivative ofa reaction product of sulfur dioxide and an aldehyde derivative of aSchiffs base.

4. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a sulfuric acid derivative ofa reaction product of sulfur dioxide and an aliphatic aldehydederivative of a Schiffs base.

5. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a sulfuric acid derivative ofa reaction product of sulfur dioxide and a material formed by reactingan aliphatic aldehyde containing less than eight carbon atoms with aprimary aromatic amine.

6. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a sulfuric acid derivative ofa reaction product of sulfur dioxide and a material formed by reactingsubstantially three molecular proportions of acetaldehyde withsubstantially two molecular proportions of aniline.

7. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a product formed by reactingsubstantially one-half a molecular proportion of sulfur dioxide withsubstantially one molecular proportion of the reaction product ofsubstantially three molecular proportions of acetaldehyde andsubstantially two molecular proportions of aniline and further reactingthe product thus formed with substantially one molecular proportion ofsulfuric acid.

8. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a product formed by reactingin the presence of acetone substantially one-half a molecular proportionof sulfur dioxide with substantially one molecular proportion of thereaction product of substantially three molecular proportions ofacetaldehyde and substantially two molecular proportions of aniline andfurther reacting the material thus formed with substantially onemolecular proportion of substantially 75% sulfuric acid.

9. A picking bath for iron and steel products comprising a sulfuric acidsolution containing a small proportion of a sulfuric acid derivative ofa reaction product of sulfur dioxide and an aldehyde-amine product.

10. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a sulfuric acidderivative of a reaction product of sulfur dioxide and an aliphaticaldehyde-aromatic-amine reaction product.

11. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a sulfuric acidderivative of a reaction product of sulfur dioxide and an aldehydederivative of a Schiffs base.

12. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a sulfuric acidderivative of a reaction product of sulfur dioxide and an aliphaticaldehyde derivative of a Schiffs base.

13. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a sulfuric acidderivative of a reaction product of-sulfur dioxide and a material formedby reacting an aliphatic aldehyde containing less than eight carbonatoms with a primary amine.

14. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a sulfuric acidderivative of a reaction product of sulfur dioxide and a material formedby reacting substantially three molecular proportions of acetaldehydewith substantially two molecular proportions of aniline.

15. A pickling bath for iron and steel products comprising asulfuricacid solution containing a small proportion of a product formed byreacting substantially one-half a molecular proportion of sulfur dioxidewith substantially one molecular proportion of the reaction product ofsubstantially three molecular proportions of acetaldehyde andsubstantially two molecular proportions of aniline and further reactingthe material thus formed with substantially one molecular proportion ofsulfuric acid.

16. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a product formed byreacting in the presence of acetone substantially one-half a molecularpropor- .252. COMPOSITIONS,

tion of sulfur dioxide with substantially one molecular proportion ofthe reaction product of substantially three molecular proportions ofacetaldehyde and substantially two molecular proportions of aniline andfurther reacting the material thus formed with substantially onemolecular proportion of substantially sulfuric acid.

17 A process of pickling a metal which comprises subjecting the metal tobe pickled to the action of a substantially non-oxidizing mineral acidsolution containing a small proportion of a sulfuric acid derivative ofa reaction product of sulfur dioxide and an aldehyde-amine product.

18. A process of pickling a metal which comprises subjecting the metalto be pickled to the action of a substantially non-oxidizing acidsolution containing a small Proportion of a sulfuric acid derivative ofa reaction product of sulfur dioxide and an ali hatic adlehyde-aromaticamine reaction pro uct.

19. A pickling bath for metal products which comprises a substantiallynon-oxidizing mineral acid solution containing a small proportion of asulfuric acid derivative of a reaction product of sulfur dioxide and analdehyde-amine product.

20. A pickling bath for metal products which comprises a substantiallynon-oxidizing mineral acid solution containing a small proportion of asulfuric acid derivative of a reaction product of sulfur dioxide and analiphatic aldehyde-aromatic amine reaction product.

In testimony whereof I hereunto aflix my signature.

DEAL H. TOMPKINS.

